[h2Olondon]

Hi guys. Due to its location the battery hold down bracket gets salt and water on to it via the front  grill. This can cause rust to form and make undoing the battery impossible quickly . These things always happen at the worse possible moment, so its worth taking precautions.
There is not much room to access the lock down bolt plus its a bit out of sight so you may not realise the bolt is rusting.
I got mine undone after penetrating oil failed by heating the bolt head with a soldering iron. This allowed the bolt to expand a bit and brake the rust locking it. Replace it with plenty of grease and check it once a year.( Dealers do not lubricate this area)
One word of caution the battery tray is plastic material I think so be careful with heating device!!

[Dazzler]

Thanks for the advice. We are so lucky they don't need to salt the roads in Australia 

[The Gonz]

Nice advice. Probably not a major concern for us Antipodeans but worthy of note. I wonder whether there's the option of using a nylon nut instead, if strong enough.

[Phil №❶]

I had the same thought, but the battery is a heavy item.

[rustynutz]

I'd be getting some marine grade stainless steel nuts/bolts.... 

[Surferdude]

It's just a bolt, Rusty. (Rusty!    )
Screws into the base the battery sits on IIRC.
But the simplest solution ( ) is to pour boiling water over it (and the battery terminals) occasionally. It'll clear the salt and any corrosion forming on the terminals.

And yes, the prevention is the best cure. A light greasing will keep all the rubbish at bay indefinitely.

[Phil №❶]

There's a waxy spray used to stop corrosion on battery terminals, I'd give it a coat of that before installing it, then recoat after